Perissodactyla: Hyracotherium, horses, rhinos & tapirs. Horses > elephants? | Perissodactyla | ||
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Perissodactyla: Hyracotherium, horses, rhinos & tapirs. Horses > elephants?
Range: from the Late Paleocene
Phylogeny: Laurasiatheria ::: Cetartiodactyla + * : Hippomorpha + Tapiromorpha.
elongate skulls; complete set of incisors; premolars molariform, often hypsodont & lophodont; horns, if present are unpaired on frontals or nasals & lack bone core; cervical vertebrae opisthocoelous; tall neural spines on thoracic vertebrae; clavicle absent; scapula is long & narrow with small coracoid process; broad, tall ilium with large gluteal (thigh) muscles; forelegs bear most weight, with hind legs providing propulsion; digits 3-4/3 (equids 1/1); "odd-toed" or mesaxonic, i.e. plane of symmetry passes through a large central digit; astragalus is primary weight-bearing tarsal; intestinal fermentation, normally requiring constant foraging, but superior use (compared to artiodactyl ruminants) of proteins and high-quality food materials.
Links: Introduction to the Perissodactyla; Fossil Horses in Cyberspace; The Tapir Gallery - Welcome!; Perissodactyla; Order Perissodactyla; Order Perissodactyla: Rhinoceroses, Horses; ISIS - taxon perissodactyla; Journal of Molecular Evolution 50: 11-21 (2000); Animal Diversity Web: Order Perissodactyla; Rhinoceros Skulls and Rhino Horns from Skulls Unlimited; Perissodactyla Hoofed (Odd-toed)); Bibliography of Ungulates: Perissodactyla and Artiodactyla, etc.; Breeds of the World; Vertebrates : Mammals : Perissodactyla; World's oldest horse runs free in Mongolia. APW020617.
Comment: : the Altungulata hypothesis, a morphology based taxon, grouping perissodactyls and paenungulates is no longer considered valid; the percieved simialties would be the result of convergence. MAK120319. Phylogeny: Ungulata: Eparctocyona + * : Hilalia + Paenungulata + (Perissodactyla + Tubulidentata)). Characters: $ petrosal does not contact basioccipital [SM98]; $ clavicle completely absent [SM98]; $ astragalar head with short neck or neck absent with flat head [SM98]; $ penial glandular fossa present [SM98]. Links: Phylo.gen; Altungulata after McKenna & Bell 1997. References: Shoshani & McKenna (1998) [SM98]. APW 020617.
Hippomorpha: Equus + Pachynolophus
Range: Ypresian (Early Eocene) [A+98] [NA00] (both based on Hyracotherium). Dominant ungulates in the Eocene.
Phylogeny: Perissodactyla : Tapiromorpha + *
References: Arnason et al. (1998) [A+98], Norman & Ashley (2000) [NA00].
Tapiromorpha: rhinos, tapirs, chalicotheres
Range: From the early Eocene
Phylogeny: Perissodactyla : Hippomorpha + *
checked ATW050727, as new page MAK120319